The invention relates to a safety belt apparatus for vehicle, in particular motor vehicles.
A safety belt apparatus is already known from GB 2 131 279 A in which the belt reel actuates a cam ring via a step down transmission. By means of a radial projection the cam ring brings the latching pawl which cooperates with the toothed ratchet wheel into engagement with the toothed ratchet wheel when the safety belt is fully drawn out and brings it out of engagement with the toothed ratchet wheel when the safety belt is fully drawn in. In this manner, after a complete draw out of the safety belt, only a pulling in of the safety belt is initially possible. This manner of operation is termed ALR operation (automatic locking retractor operation). After full draw in of the belt, the latching pawl is released by the toothed latching wheel so that now a free draw out of the belt is possible. A draw out blocking mechanism now only enters into operation if an attempt is made to pull the belt out rapidly or if accelerations caused by an accident occur. This manner of operation is termed ELR operation (emergency locking retractor operation).
In this known apparatus the movement of two rotary blocking pawls into a surrounding toothed ring fixed relative to the housing on attempted rapid belt pull out takes place in that a rotary clearance is provided between the belt reel and a toothed ratchet wheel and is removed by a spring acting between the belt reel and the toothed ratchet wheel, until, on attempted belt pull out, a pre-determined rotary acceleration value is exceeded, which leads to the rotation of the toothed ratchet wheel lagging behind the rotation of the belt reel, whereby movement of the blocking pawls into engagement is brought about. A precondition for the operability of the known pull out blocking mechanism is thus that the toothed ratchet wheel rotates with delay relative to the belt reel above a predetermined rotary acceleration value. Problematic with this design of the pull out blocking mechanism is the fact that the relative angular position in which the blocking pawls move towards the surrounding inner ring of teeth fixed relative to the housing cannot be determined in advance. Should the teeth of the blocking pawl and of the inner toothed arrangement by chance stand tooth to tooth during the movement into engagement, then an engagement of the pawl teeth into the tooth recesses of the inner ring of teeth is not possible. Thereafter, an engagement of the blocking pawl into the tooth recesses of the inner ring of teeth is also not ensured with the required certainty as a result of the generally high speed of rotation of the belt reel.
EP 0 298 123 A1 describes a safety belt apparatus in which the transmission which acts on the cam ring is formed as a cycloidal transmission, such as is also used in a safety belt apparatus known from U.S. Pat. No. 5,518,197.
A transmission of this kind is also provided in a safety belt apparatus for motor vehicles (DE 196 48 515 A1), with the cam ring only being rotated through a smaller angle in the end positions of the rotating toothed control wheel, which is just sufficient in order to bring the blocking pawl into or out of engagement with the toothed ratchet wheel. In this known apparatus the inner toothed ring and the toothed control wheel are preferably so formed that the toothed control wheel can execute about a one half revolution between full belt draw in and full belt draw out.
In all previously known safety belt apparatuses with a switching cam ring, the latter has the task of bringing the preferably resiliently deflectable blocking pawl into or out of engagement with the toothed ratchet wheel connected to the belt reel.
The object of the present invention is to provide a further safety belt apparatus of the initially named kind in which the cam ring in particular is better exploited.
The concept underlying the invention is thus to be seen in the fact that at least one further switching function is associated with the cam ring in addition to the function of bringing the resiliently deflectable blocking pawl into and out of engagement with the toothed ratchet wheel in defined manner.
This is achieved in that the periphery of the cam ring is subdivided into a plurality of regions, preferably two regions, of which only one takes on the blocking pawl switching function, whereas the other is available for triggering of further switching functions. Since, in accordance with the invention, a part region of the periphery of the cam ring is to be available for other than blocking pawl switching purposes, the angular region which is available for the blocking pawl switching should be about 180xc2x0 or somewhat more (up to ca. 200xc2x0). The remainder of the periphery of the cam ring can then be designed, for example, with magnetic, electrical and/or mechanical elements, so that one or more further switching functions are triggered at specific angles of rotation of the cam ring. For this purpose stationary elements, such as mechanically, electrically or magnetically actuated switches are provided radially opposite to the relevant part of the peripheral surface and cooperate with the associated elements on the cam ring.
A special embodiment of the present invention makes provision for a belt tensioner to be activated or deactivated by the additional peripheral surface on the cam ring. It is namely expedient to deactivate a belt tensioner with a non-applied, i.e. drawn-in safety belt, and to first activate it when it has been pulled out by a predetermined amount which is not, however, sufficient in order to be placed around the occupant to be protected. In this manner it is ensured that the belt tensioner is in any event activated after being placed onto an occupant to be protected. Through the invention, the respective activation or deactivation can be effected by the same cam ring which is already responsible for the movement of the blocking pawl in and out of engagement.
A preferred practical realization of the concept of the invention includes the use of a tilting element brings about the advantage that a once set blocking pawl position is maintained until a counter-force acts on the tilting element.
The rotationally fixed and simultaneously radially displaceable connection of the toothed control wheel to the cam ring expediently takes place in accordance with features of the invention described further below.
In order to avoid the disadvantages associated with the pull out blocking mechanism of GB 2 131 279 A, the invention provides the certain features. In this manner the trouble-free movement of the teeth of the engageable pawl into the surrounding inner ring of teeth can be ensured, since a fixed and predeterminable angular relationship exists between the angles at which the toothed ratchet wheel is stopped by the blocking tooth and the position of these engageable pawl. The features are a precondition for the precise movement of the engageable pawl into engagement, i.e. that on exceeding the predetermined acceleration boundary value of the belt reel, and with the belt pull out acceleration which normally prevails, the speed of rotation of the toothed ratchet wheel does not lag behind that of the belt reel. In this way an undefined engagement of the engageable pawl into the surrounding inner toothed arrangement is reliably avoided. With extremely large belt pull out accelerations caused by an accident, a rotation of the toothed ratchet wheel is in any event stopped by the generally provided blocking mechanism for the toothed ratchet wheel, which responds to pronounced vehicle accelerations or decelerations and large deviations of the vehicle from the horizontal position. In this case the belt pull out blocking mechanism is thus not required.